Coherent photoproduction of the neutral pion and eta meson on the deuteron, \(\gamma {d}\) \(\rightarrow \)\(\pi ^0\eta {d}\), has been experimentally studied at \(E_\gamma <1.15\) GeV. The total cross section as a function of the incident energy shows a rapid increasing behavior below 1 GeV. The existing theoretical calculations well-reproduce the data including final-state interactions. We have measured the differential cross sections \(d\sigma /dM_{\pi d}\), \(d\sigma /dM_{\eta d}\), and \(d\sigma /d\Omega _d\) in the \(\gamma d\) center-of-mass frame for the first time. An enhancement is observed near the \(\eta d\) threshold in \(d\sigma /dM_{\eta d}\), suggesting a strong \(\eta d\) attraction. The enhancement is consistent with a predicted isoscalar \(1^-\) \(\eta NN\) bound state from the \(\eta NN\) and \(\pi NN\) coupled-channel calculation.

氘核上的中性介子和 eta 介子的相干光产生\(\gamma {d}\) \(\rightarrow \) \(\pi ^0\eta {d}\)已在\(E_ \gamma <1.15\) GeV。作为入射能量的函数的总横截面显示出低于 1 GeV 的快速增加行为。现有的理论计算很好地再现了包括终态相互作用在内的数据。我们测量了差分横截面\(d\sigma /dM_{\pi d}\)、\(d\sigma /dM_{\eta d}\)和\(d\sigma /d\Omega _d\)第一次在\(\gamma d\) 质心坐标系中。在\(\eta d\)附近观察到增强\(d\sigma /dM_{\eta d}\) 中的阈值，表明强烈的\(\eta d\)吸引力。增强与来自\(\eta NN\)和\(\pi NN\)耦合通道计算的预测等标量\(1^-\) \(\eta NN\)绑定状态一致。